1991 BMW 525i • 225,000 miles

The battery went down on my 1991 BMW 525i after having sat for a year; over which time I replaced the factory radio with an aftermarket stereo. After charging the battery, I have found that the car is immobilized mode with the alarm sounding. I have tried entering a 4 diget code in the OBC to disarm the alarm but it will not reset. I've even tried disconnecting the battery and touching the cables together for 30 seconds, but to no avail. I would rather do away with the alarm system all together. Can someone please tell me how to either remove of reset the system PLEASE!
October 21, 2012.

Factory or aftermarket?


Oct 21, 2012.
A stock alarm is removable and the unit resides in the area around the glove box and is accessed through the under dash on the passenger side. Just disconnect it and the problem should be solved. Let us know if you have questions, Dr. Hagerty

Dr. Hagerty
Oct 22, 2012.
Just to clarify, you should be looking for a control unit (box, usually black or silver) with a 20-40 pin connectors, one of which might be just black and red for power, 4 for door locks, and 10-15 for sensors and other controls.

I also show a "general module' in the passenger compartment fuse/relay block.

Oct 23, 2012.
Since my original question regarding my immobilization alarm question, I have since changed out the OBC. The alarm has stopped and now the display says: PPPP what do I do Now?

Oct 25, 2012.
New update: OBC is functional now but still no ignition or radio function. Next step?

Oct 26, 2012.
1. With the car and power off, plug in the new OBC unit.

2. Turn car power on with key, but do not start car (radio works but ignition is not cranked.)

3. Push the "Code" button.

4. Push the S/R button.

5. Now without powering the car electrical system down, start the car.

6. Program your new unit which should be displaying 00.00 for the time setting.

Oct 27, 2012.